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Abstract:

An RC test circuit includes an RC circuit, a digital rheostat, a control
chip, and an oscillograph. The RC circuit includes a plurality of
positive terminals and a plurality of negative terminals. The digital
rheostat includes a plurality of rheostats each including a sliding
terminal and a fixed terminal. The sliding terminals are correspondingly
connected to the positive terminals while the fixed terminals are
correspondingly connected to the negative terminals. The control chip is
connected to the digital rheostat, and configured for controlling the
digital rheostat to change the resistance of each rheostat. The
oscillograph is connected to the RC circuit for displaying a waveform of
the RC circuit.

Claims:

1. An RC test circuit, comprising: an RC circuit comprising a plurality
of positive terminals and a plurality of negative terminals; a digital
rheostat comprising a plurality of rheostats each comprising a sliding
terminal and a fixed terminal, the sliding terminals correspondingly
connected to the positive terminals while the fixed terminals
correspondingly connected to the negative terminals; a control chip
connected to the digital rheostat, and configured for controlling the
digital rheostat to change resistance of each rheostat; and an
oscillograph connected to the RC circuit for displaying a waveform of the
RC circuit.

2. The RC test circuit of claim 1, further comprising a display device
for displaying the resistance of each rheostat of the digital rheostat.

3. The RC test circuit of claim 1, wherein the control chip comprises a
RA0 terminal, a RA1 terminal, a RA2 terminal, a RA3 terminal, the RA0-RA3
terminals are connected to the display device, to continuously output a
plurality of resistance value signals from the digital rheostat to the
display device, so that the display device can display the resistance
values of the digital rheostat.

4. The RC test circuit of claim 1, wherein the control chip comprises a
RB0 terminal, a RB1 terminal, a RB2 terminal, and a RB3 terminal, the
RB0-RB3 terminals are connected to the digital rheostat to output a
plurality of control signals to the digital rheostat and control the
digital rheostat to change resistances thereof.

5. The RC test circuit of claim 4, wherein the control chip comprises a
RC0 terminal, a RC1 terminal, a RC2 terminal, a RC3 terminal, a RC4
terminal, a RC5 terminal, and a RC6 terminal, the RC0-RC6 terminals are
connected to a peripheral input device to input the control signals and
transfer the control signals to the RB0-RB3 terminals.

6. The RC test circuit of claim 5, wherein the digital rheostat comprises
an A0 terminal, an A1 terminal, and an A2 terminal, the A0-A3 terminals
are correspondingly connected to the RB0.about.RB3 terminals, and
configured to input the corresponding control signals from the control
chip to the first rheostat, the second rheostat, and the third rheostat.

7. The RC test circuit of claim 5, wherein the peripheral input device is
a keyboard.

8. The RC test circuit of claim 1, wherein the control chip comprises a
first serial clock (SCL) terminal, and a first serial data (SDA)
terminal, the digital rheostat comprises a second SCL terminal, and a
second SDA terminal, the second SCL terminal and the second SDA terminal
are correspondingly connected to the first SCL terminal and the first SDA
terminal

9. The RC test circuit of claim 5, wherein the control chip comprises at
least one memory and at least one adder-subtractor in communication with
the at least one memory, a current resistance value of the digital
rheostat is stored in the at least one memory, the at least one
adder-subtractor is configured for receiving the input resistance values
from the peripheral input device, and calculating the sum or difference
between the input resistance value and the corresponding current
resistance value.

10. The RC test circuit of claim 9, wherein the digital rheostat
comprises a first rheostat, a second rheostat, and a third rheostat, the
first rheostat comprises a first sliding terminal and a first fixed
terminal, the second rheostat comprises a second sliding terminal and a
second fixed terminal, the third rheostat comprises a third sliding
terminal and a third fixed terminal, the digital rheostat is configured
for respectively changing the resistances of the first rheostat, the
second rheostat and the third rheostat by respectively changing the
resistances between the first sliding terminal and the first fixed
terminal, between the second sliding terminal and the second fixed
terminal, and between the third sliding terminal and the third fixed
terminal.

11. The RC test circuit of claim 10, wherein the peripheral input device
comprises three control sections to respectively input the resistance
values, the control chip introduces three memories and three
adder-subtractors individually communicating with the three control
sections and establish three signal channels 19, the three signal
channels 19 are respectively connected to the first rheostat, the second
rheostat, and the third rheostat, to transfer the control signals to the
first rheostat, the second rheostat, and the third rheostat.

12. The RC test circuit of claim 1, wherein the RC circuit comprises a
first RC sub-circuit, a second RC sub-circuit, and two output terminals
connected to the first RC sub-circuit and the second RC sub-circuit, the
two output terminals are correspondingly connected to two test probes of
the oscillograph, the first RC sub-circuit comprises a first position for
positioning a first resistor therein, a second position for positioning a
second resistor therein, and a first capacitor, the first capacitor is
connected to the first resistor in series and connected to the second
resistor in parallel, the second RC sub-circuit comprises a third
position for positioning a third resistor therein, a second capacitor,
and a third capacitor, the third capacitor is connected to the third
resistor in series and connected to the second capacitor in parallel.

13. The RC test circuit of claim 12, wherein each of the first, second,
and third positions comprises the positive terminal and the negative
terminal, the positive terminal of the first position is connected to the
first sliding terminal, the positive terminal of the second position is
connected to the second sliding terminal, and the positive terminal of
the third position is connected to the third sliding terminal, the
negative terminal of the first position is connected to the first fixed
terminal, the negative terminal of the second position is connected to
the second fixed terminal, and the negative terminal of the third
position is connected to the third fixed terminal.

Description:

BACKGROUND

[0001] 1. Technical Field

[0002] The present disclosure relates to resistor-capacitor (RC) circuits,
and particularly, to a test circuit capable of efficiently testing
resistance of resistors of an RC circuit.

[0003] 2. Description of Related Art

[0004] In an RC circuit, resistance of resistors of the RC circuit can
greatly affect stability of the entire RC circuit. Therefore, in the
design of the RC circuit, resistors of varying resistances are placed in
the RC circuit in turn to test stability of the RC circuit at a desired
performance. However, in this process, it is required to manually change
out each resistor every time, which can be time consuming and
inconvenient.

[0005] Therefore, it is desirable to provide RC test circuit which can
overcome the problems described above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 is a functional block diagram of a RC test circuit,
according to an exemplary embodiment.

[0007] FIG. 2 is a circuit diagram of one embodiment of the RC test
circuit of FIG. 1.

DETAILED DESCRIPTION

[0008] Exemplary embodiments of the disclosure will now be described in
detail, with reference to the accompanying drawing.

[0009] FIG. 1 is a functional block diagram of a RC test circuit 100,
according to an exemplary embodiment. The RC test circuit 100 includes a
control chip 10, a digital rheostat 20, and a RC circuit 30. The control
chip 10 is electronically connected to the digital rheostat 20, while the
digital rheostat 20 is integrated in the RC circuit 30. The digital
rheostat 20 is configured to replace a number of resistors (detailed
below) of the RC circuit 30, to vary resistance of the RC circuit 30
according to operations by user or a preset program of the control chip
10.

[0010] The control chip 10 is a programmable processing unit, and includes
a RA0 terminal, a RA1 terminal, a RA2 terminal, a RA3 terminal, a RB0
terminal, a RB1 terminal, a RB2 terminal, a RB3 terminal, a RC0 terminal,
a RC1 terminal, a RC2 terminal, a RC3 terminal, a RC4 terminal, a RC5
terminal, a RC6 terminal, a first serial clock (SCL) terminal, and a
first serial data (SDA) terminal.

[0011] The RA0-RA3 terminals are electrically connected to a display
device 11, to continuously output a number of resistance value signals
from the digital rheostat 20 to the display device 11, so that the
display device 11 can display the resistance values of the digital
rheostat 20. The RB0-RB3 terminals are connected to the digital rheostat
20 to output a number of control signals to the digital rheostat 20. The
control signals signal the digital rheostat 20 to change resistance of
the digital rheostat 20. The RC0-RC6 terminals are input/output (I/O)
type terminals and connected to a peripheral input device 13, to input
the control signals from the peripheral input device 13 and transfer the
control signals to the RB0-RB3 terminals. In this embodiment, the
peripheral input device 13 is a keyboard, the control signals are
translated from a number of input resistance values implemented on the
keyboard. In particular, the peripheral input device 13 includes three
control sections 131 for respectively inputting the resistance values.
The control area is defined to as an operation/inputting area that can
trigger a function of the control chip 10, such as the number pad of the
keyboard.

[0012] The control chip 10 includes at least one memory 15 and at least
one adder-subtractor 17 in communication with the at least one memory 15.
In this non-limiting embodiment, three memories 15 and three
adder-subtractors 17 are introduced, to individually communicate with the
three control sections 131 of the peripheral input device 13 and
establish three signal channels 19. Each signal channel is configured to
transfer signals through the corresponding control area, the memory, the
adder-subtractor, and the digital rheostat 20. As such, the control
signals from the peripheral input device 13 can be individually
transferred to the digital rheostat 20 via the three signal channels 19,
thereby reducing signal interference and making the signal processing
easier. A current resistance value of the digital rheostat 20 is stored
in each memory 15. The adder-subtractors 17 are configured for receiving
the input resistance values from the peripheral input device 13, and
calculating the sum or difference between the input resistance value and
the corresponding current resistance value. For example, if the current
resistance value has a maximum value of 10 kΩ, and if the input
resistance value is 1 kΩ every time, then the adder-subtractor 17
will control the current resistance value 10 kΩ to minus 2
kΩ, then output an 8 kΩ to the display device 11. As
mentioned above, the 1 kΩ value can be inputted by a keyboard. In
other embodiments, the input resistance values can be chosen as
10Ω, 100Ω or other numbers.

[0013] The digital rheostat 20 includes a first rheostat 21, a second
rheostat 22 and a third rheostat 23. The first rheostat 21, the second
rheostat 22 and the third rheostat 23 are individually in communication
with the three channels of the control chip 10, to respectively receive
the control signals from the peripheral input device 13. In additional,
the display device 11 can respectively display the resistance values of
the first rheostat 21, the second rheostat 22, and the third rheostat 23
according to the control signals.

[0014] The first rheostat 21 includes a first sliding terminal VM0 and a
first fixed terminal VL0. The second rheostat 22 includes a second
sliding terminal VM1 and a second fixed terminal VL1. The third rheostat
23 includes a third sliding terminal VM2 and a third fixed terminal VL2.
In the present embodiment, the first sliding terminal VM0 is adjacent to
the fixed terminal VL0. The second sliding terminal VM1 is adjacent to
the second fixed terminal VL1. The third sliding terminal VM2 is adjacent
to the third fixed terminal VL2. The digital rheostat 20 is configured
for changing the resistances of the first rheostat 21, the second
rheostat 22 and the third rheostat 23 by respectively changing the
resistances between the first sliding terminal VM0 and the first fixed
terminal VL0, between the second sliding terminal VM1 and the second
fixed terminal VL1, and between the third sliding terminal VM2 and the
third fixed terminal VL2.

[0015] The digital rheostat 20 further includes an A0 terminal, an A1
terminal, an A2 terminal, an A3 terminal, a second SCL terminal, and a
second SDA terminal. The A0-A3 terminals are correspondingly connected to
the RB0˜RB3 terminals, while the second SCL terminal and the second
SDA terminal are correspondingly connected to the first SCL terminal and
the first SDA terminal of the control chip 10. In this embodiment, the
A0-A3 terminals are address terminals. The A0-A3 terminals can input the
corresponding control signals from the control chip 10 to the first
rheostat 21, the second rheostat 22, and the third rheostat 23, to change
the resistances of the first rheostat 21, the second rheostat 22, and the
third rheostat 23.

[0016] The RC circuit 30 includes a first RC sub-circuit 31, a second RC
sub-circuit 33, and two output terminals V0 connected to the first RC
sub-circuit 31 and the second RC sub-circuit 33. The two output terminals
V0 are correspondingly connected to two test probes of an oscillograph
35.

[0017] The first RC sub-circuit 31 includes a first position for
positioning a first resistor R1 (shown in broken line in FIG. 2) therein,
a second position for positioning a second resistor R2 therein, and a
first capacitor C1. The first capacitor C1 is connected to the first
resistor R1 in series and connected to the second resistor R2 in
parallel. The second RC sub-circuit 33 includes a third position for
positioning a third resistor R3 therein, a second capacitor C2, and a
third capacitor C3. The third capacitor C3 is connected to the third
resistor R3 in series and connected to the second capacitor C2 in
parallel. Each of the first position, second position, and the third
position can include a node used for soldering a corresponding resistor
thereon, and includes a positive terminal (+) and a negative terminal
(-). The positive terminals (+) of the positions are configured to
correspondingly connect to the fixed terminals VL0-VL2. The negative
terminals (-) of the positions are configured to correspondingly connect
to the sliding terminals VW0-VW2. In particular, the positive terminal
(+) of the first position is connected to the first sliding terminal VW0,
the positive terminal (+) of the second position is connected to the
second sliding terminal VW1, and the positive terminal (+) of the third
position is connected to the third sliding terminal VW2. The negative
terminal (-) of the first position is connected to the first fixed
terminal VL0, the negative terminal (-) of the second position is
connected to the second fixed terminal VL1, and the negative terminal (-)
of the third position is connected to the third fixed terminal VL2. More
specifically, in this embodiment, the positive terminals (+) and the
negative terminals (-) are connected to the fixed terminal VL0 to VL2 and
sliding terminals VW0 to VW2 via twisted pairs.

[0018] During the testing process of the RC circuit 30, according to the
preset program or manual operations on the keyboard, the control chip 10
changes the resistances of the first rheostat 21, the second rheostat 22,
and the third rheostat 23 according to the control signals. In this
embodiment, the resistances of the first rheostat 21, the second rheostat
22, and the third rheostat 23 are increased from a minimum value. In
other embodiments, the resistances of the first rheostat 21, the second
rheostat 22, and the third rheostat 23 are decreased from the maximum
value or increased/decreased from a middle value. As such, the resistance
of the RC circuit 30 is changed with the changing of the resistances of
the first rheostat 21, the second rheostat 22, and the third rheostat 23.
Meanwhile, the oscillograph 35 displays a waveform of a series of output
signals from the RC circuit 30, according to the changeable resistance of
the RC circuit 30. When the waveform meets the requirements of the user,
the resistances of the first rheostat 21, the second rheostat 22, and the
third rheostat 23 are confirmed to be the best match, and the display
device 30 displays only the resistances of the first rheostat 21, the
second rheostat 22, and the third rheostat 23 at that time. After reading
the resistances of the first rheostat 21, the second rheostat 22, and the
third rheostat 23, the digital rheostat 20 is removed and the first
resistor R1, the second resistor R2, and the third resistor R3
respectively corresponding to the first rheostat 21, the second rheostat
22, and the third rheostat 23 are placed to the first position, the
second position, and the third position. As such, the RC circuit 30 can
be completely designed.

[0019] It is understood that the control chip 10 can employ only one
memory 15 and only one adder-subtractor 17, depending on the number of
the rheostats of the digital rheostat 20.

[0020] It will be understood that particular exemplary embodiments and
methods are shown and described by way of illustration only. The
principles and the features of the present disclosure may be employed in
various and numerous exemplary embodiments thereof without departing from
the scope of the disclosure as claimed. The above-described exemplary
embodiments illustrate the scope of the disclosure but do not restrict
the scope of the disclosure.